He then stopped the sound source for a moment, and the matter at once began to slide downwards, falling as matter normally should when on a vertical surface; however, when he turned the sound back on, the matter proceeded to climb back up the plate, and reform perfectly into the cymatics patterns it had been holding previously.

The matter then remained clinging to the vertical surface, oscillating to the sound waves and seeming to “defy gravity” as it hung above the earth in beautiful cymatic symmetry.

I don’t think it defies gravity per say but I do think it does quite the opposite, I think we are just able to manifest the potential of sound through gravity(even though gravity manifest from sound)
Because through space nothing would holds sound except matter and matter resonates.
I think gravity is an emergent property of sound or vibration and that we see the patterns present through cymatics which I think inherently is but just the representation we see through all life on the planet.
I think if we see persistent patterns with sound and even see those phenomenon representing life, how can we not say that gravity played a role in form both phenomenon because it is the same phenomenon.